DUBLIN — With a flip of the switch, Alameda County and energy officials “activated” the new fuel cell power plant at the Santa Rita jail Thursday, even though the power plant has been running at full power since May 30.

The ceremony was part of a dedication attended by more than 100 county, state and private sector officials. Santa Rita jail is the fifth-largest jail in the country and the third largest in the state. It currently serves about 3,800 inmates.

The plant is expected to save taxpayers $266,825 annually on the jail’s electric bill.

“Alameda County is an example we would like to see replicated throughout the state of California,” said Bruce Ludemann, a vice president of sales atFuelCell Energy Inc., which designed and built the power plant next to the jail. “It transforms fuel into energy without burning.”

A fuel cell plant, in layman’s terms, is similar to a giant, continuously running battery. It takes fuel and turns it into energy without combustion by pulling out the hydrogen and combining it with oxygen.

A Sacramento-based clean-energy advocate, Bernadette Del Chiaro of Environment California, applauded the new power plant, calling it “the wave of the future.”

It’s good to see government agencies being leaders on this,” she said. “Instead of building a giant coal-fired plant out in the middle of nowhere and having the rest of us pool our resources on transmission lines, it’s better to create technologies that sit right on the site.”

Besides energy, the fuel cell plant creates “waste heat.”

Jim Davis, president of Chevron Energy Solutions, which integrated the power plant with the jail, said this particular power plant is more efficient than others.

“Chevron designed this … to capture waste heat,” Davis said.

The power plant is able to take the waste and use it to heat water and various spaces throughout the jail.

“This brings many good things for the environment,” Davis said.

At one megawatt, the power plant is the first of its kind in size in California. It will generate 8 million kilowatt hours of electricity, about half of the jail’s needs. Along with the solar panels on the jail’s roof, which provide the other 50 percent, all of the jail’s energy is now “green” energy.

The fuel cell will have 98.5 percent lower nitrogen oxide emissions than standard power plants, the equivalent of planting 900 acres of trees, officials said.

“You’re going to be amazed how small it is compared to the power it generates,” Assistant Sheriff Robert Maginnis said. “This is, indeed, the future.”

At the dedication, a PG&E representative presented a check for about $1.4 million to the county as part of its incentive program for the jail’s switch to self-generating energy production.

Construction on the fuel cell power plant began in November 2005 and cost about $6 million.